1. Field of the Invention
The present invention relates in general to the field of information handling system thermal control, and more particularly to information handling system thermal control by energy conservation.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems are typically built by assembling a variety of components into a chassis so that the components cooperate to process information. For example, a blade server information handling system has a chassis that accepts plural blade server modules by sharing power and networking resources of the chassis with the blade servers under the control of a chassis management controller (CMC). Each blade server module typically has a motherboard with one or more central processing units (CPUs), power distribution circuits, persistent storage devices like hard disk drives or solid state drives, memory like DRAM, networking components, mezzanine cards and a baseboard management controller (BMC) that provides management functions like remote power-up and power-down. The chassis management controller manages power resources by distributing power allocations to the blade modules. A baseboard management controller on each blade module powers components within the blade module to operate within the power allocation budget provided by the chassis management controller. The chassis management controller also typically manages cooling resources provided by a fan controller and one or more cooling fans based upon thermal information provided from the baseboard management controllers, such as thermal measurements at components within each blade module. In server information handling systems, a bulk air temperature represented by the temperature of a cooling airflow exhaust is sometimes managed by adjusting fan speed to maintain less than a maximum exhaust temperature.
One difficulty with management of thermal conditions in an information handling system chassis is that thermal conditions tend to vary throughout a chassis enclosure. Variance in thermal conditions can be significant in a modular information handling system, such as a blade information handling system, where a particular module has a higher workload than other modules in the same chassis. Variance in thermal conditions can also be significant across an information handling system module where different components of the module operate at varying workloads. For example, thermal conditions near a central processing unit typically increase during the performance of processing-intensive operations. In order to monitor thermal conditions at processors, processors typically incorporate a thermal sensor, such as a thermistor, and logic to report thermal conditions measured by the thermal sensor to a system thermal manager, such as firmware instructions running on a BIOS, BMC, CMC, and/or fan controller that manages cooling fan operating speeds. Processors are typically physically located “upstream” of a cooling airflow provided by a cooling fan to provide efficient cooling since processors generally are one of the greatest sources of thermal energy in a chassis and also usually among the most heat sensitive of components. Other components are typically disposed in the chassis “downstream” of the processor so that cooling airflow passes by the processor first and then passes by less-heat sensitive components.
One difficulty with managing thermal conditions in an information handling system chassis enclosure is that not all components integrate thermal self-protection capabilities in order to maintain reliability conformance during thermal excursions, such as when a cooling system fails, extreme ambient environmental temperatures exist or ultra-high stress operating conditions exist that exceed the capabilities of a chassis' cooling system. For example, a processor operating in extreme thermal conditions will throttle its power consumption to reduce heat generation and maintain its internal temperature within a desired constraint; however, mezzanine cards, some hard disk drives and many on board devices like networking, chipset, power distribution and BMC devices, do not include thermal sensors or thermal self-protection capabilities. Since these thermally “helpless” components are often downstream of a cooling airflow, the three primary ways of ensuring adequate cooling of “helpless” components are to throttle the helpless components, to increase fan speeds so that a greater cooling airflow exists to remove excess thermal energy or to throttle upstream components so that less thermal energy is generated to reduce the downstream cooling airflow temperature. Unfortunately, if components do not have thermal sensors then no direct measurement of thermal conditions at the components exists to provide direct control over thermal conditions at the component.
In order to manage thermal conditions within an information handling system chassis for components that do not include thermal sensors, some information handling systems dispose thermal sensors near components that monitor localized air temperatures. Unfortunately, as air flows through an information handling system enclosure, air streamlines across the enclosure can have significant variation in temperature even across small linear separations. In chassis enclosures that include plural modules, such as a blade chassis, an exhaust temperature of a cooling subsystem that cools plural modules does not necessarily indicate thermal conditions at any one module because different modules often run different loads. For example, a module running at a high load can have extreme thermal conditions even though the bulk temperature of a cooling subsystem exhaust is in a normal range. One solution for thermal management of components that lack thermal sensors is to nest a large array of onboard thermistors to average thermal readings for a more accurate “bulk” air temperature. This solution tends to increase system cost by the addition of plural interfaced sensors and system complexity by having multiple thermal measurements and multiple failure points.